1. Field of the Invention
The present invention relates to a method of detecting remotely full duplex/half duplex mismatches in an Ether network. More specifically, the method enables detecting remotely the presence of a duplex mismatch between a full duplex/half duplex mismatch detecting apparatus and a host (a network apparatus such as a personal computer, a router or a switch) to be checked, by connecting the detecting apparatus to a network. The invention relates to a full duplex/half duplex mismatch detecting method and a full duplex/half duplex mismatch detecting apparatus applicable with the method.
2. Description of the Related Art
A full duplex/half duplex mismatch (duplex mismatch) occurs when an automatic negotiation has failed between apparatuses using an Ether network. Then, packets passing through the line on which the mismatch has occurred are destroyed and this causes packet loss consequently. Though the communication on the line is possible even when a mismatch has occurred on the line, the mismatch seriously influences the performance of applications such as HTTP (Hyper Text Transfer Protocol) and FTP (File Transfer Protocol) that handle a large amount of traffic because the performance is significantly degraded due to intermittent packet loss.
Using a “ping command” is common as a method of detecting packet loss in an IP network. However, in principle, the ping command alone can not cause the loss to occur even when a duplex mismatch has occurred and, therefore, the duplex mismatch has not been able to be detected consequently using the ping command.
Therefore, at present, when loss has occurred in communications on a protocol such as UDP (User Datagram Protocol) and TCP (Transmission Control Protocol), it is common to check duplex mismatches by inspecting the mode of the duplex (whether full duplex or half duplex) of the interfaces of all of such apparatuses on the communication path as routers, switches and hosts.
Furthermore, as a conventional technique, it is known that a server that can download to clients an application that detects duplex mismatches is installed in a network and, by analyzing the TCP sequence between a server and a client and detecting that the loss rates are asymmetric between the uplink line and the downlink line when a duplex mismatch has occurred because the TCP traffics are asymmetric between the uplink line and the downlink line, the duplex mismatch is discovered. (See, for example, “Detecting Duplex Mismatch on Ethernet”, http://www.pan2005.org/PDF/34310138.pdf)
However, in the above conventional method of checking a duplex mismatch by inspecting the mode of the duplex (whether full duplex or half duplex) of the interfaces of all of such apparatuses on the communication path as routers, switches and hosts, the following preconditions need to be cleared in order to inspect the interface status of those apparatuses.    1) The connection topology among the network apparatuses is known.    2) Means for checking the mode of duplex of the network apparatuses is possessed as knowledge.    3) A human can move to a place where the human can check the duplex mode.
In addition to the above, the status of the mode of duplex needs to be actually checked manually for each of the network apparatuses and this results in a problem that the cost becomes high in terms of personnel and time.
Furthermore, in the technique described in the above reference, the case where loss has occurred from the asymmetry between the uplink line and the downlink line without any duplex mismatch and the case where a duplex mismatch has actually occurred, can not be distinguished from each other and a duplex mismatch may be determined mistakenly. Furthermore, because the technique employs a system for which a server needs to be prepared, all clients need to access the server and a hundred clients, for example, has to be operated in order to check those hundred clients. Therefore, the technique has a problem of higher cost for checking.